While I sympathise with the OP,s story about having his wheel nicked, I think its a bit cheeky to pop up on here and ask for one for free, or as near free as possible. Or is it just me ?

Mig

Ouch! You may have missed that I offered to pay for it.

I thought how many Omegas (and other cars) must go to the scrapyard, as my previous one did, with a spare wheel which had never been used and which was worthless to the scrapyard as no-one needs to buy a replacement spare wheel.

195/65r15 on steel wheels are very popular 5x110 PCD fit astra,vectra(as you know ) zafira A & B,and many other vauxhall and saabs so why say "worthless to the scrapyard as no-one needs to buy a replacement spare wheel"most breakers yards remove all good tyres and alloys ,sell tyres and alloys separate

You will have discovered by now that I am a bit of a twit not least because I mistyped the size I think my spare should be The wheels are of course R16 and not R17. I have no idea what the other parameters should be. In my defence may I say that I don't have the spare to hand to check.

I still have four wheels on the car where I can read the tyres and they all say 225 55 R16.

I was therefore guessing that my long gone spare was (is - it's just it and I are no longer living together) 205 65 R16.

Which do I need - 195/65/15 or 205/55/16? I figure I am best to go for the 195/65/15 as it will be narrower for the well, and it is only a "get you home" tyre. 195*65% = 127 whereas 225*55% is 124 which is quite reasonable.

Which do I need - 195/65/15 or 205/55/16? I figure I am best to go for the 195/65/15 as it will be narrower for the well, and it is only a "get you home" tyre. 195*65% = 127 whereas 225*55% is 124 which is quite reasonable.

A quick lesson:

205/55 R 16:

205 is the nominal width of the tread in mm. Nominal because it varies a bit between brands.

55 is the aspect ratio - the height of the sidewall as a percentage of the tread width.

R is the speed rating, but it's not the whole story as there will be a W,H or V marked elsewhere that goes with it. You must not fit a lower speed rated tyre than the car is capable of.

16 is the diameter of the wheel in inches.

7J 15 relates to the wheel(an Omega one is more likely to be 6J 15), which means 7inches wide and 15 inch diameter. You might also see something like 38ET quoted; that is the offset, and it's where the mounting face of the wheel compared to one edge(I can't remember which, but it's probably the inner as that has to clear the suspension). You can fit a very wide range of tyre widths and sizes to this width wheel.

You are not supposed to mix tyre sizes on the same axle(it's illegal), but a spacesaver spare does just that by juggling tyre width/aspect ratio/diameter to give what is basically the same overall diameter(rolling radius). It is still considered a spacesaver for temporary use even if it's a normal tyre size or wheel and will have a sticker that says so. Which makes a 195/65 15" tyre on a steel wheel, that was fitted to all four corners of original poverty spec Omegas, a spacesaver on all others. That size was very common on Granadas, Mercs, BMWs and other largish cars in the late eighties and through the nineties until we were all brainwashed into wanting massive diameter low profiles for some reason.

What this means is that ideally you want a spare wheel and tyre that is exactly the same size, width, diameter, speed rating as the ones on the car. You can do that without any problems on an estate, as the wheel well takes all of the stock size wheels and tyres. This isn't necessarily true of saloons but if I had one on 16s, I'd be looking for one of those and living with the tighter fit and not having the cover on it.

195/65R15 is the same rolling radius as 205/55R16 the later being 10mm wider so your spare should be 195.65 r15 on a steel 5x 110mm PCD GM rim legal tread and not cracked.holds air IIRC with the spare fitted you should limit speed to 80 KM/h or 50 MP/h

Thanks for that lesson, Nick.I presume wheels are shaped so that tyre centre lines coincide with the steering centre lines (the 'offset?).If Omega steel spare wheels will fit my Vectra, I reckon all Omega wheels should do so. Right?

I still have four wheels on the car where I can read the tyres and they all say 225 55 R16.

I was therefore guessing that my long gone spare was (is - it's just it and I are no longer living together) 205 65 R16.

225/55-R16 95W or 94V on 7J x 16" (ET 33) alloys were standard fit on estates. Is yours an estate or a saloon?That size is standard for later saloons as well.205/65-R15 94V on 6.1/2J X 15" (ET 33) steel is the standard spare for facelift estates.A wider tyre or a wider rim would not fit in the wheel-well. And probably not in a saloon either.

So the spare you lost was very likely a 205/65-R15 94V on a 6.1/2J x 15" steel wheel. This is a very close match on rolling radius to the main wheels. And seems the most likely spare supplied for all but some base models, which might have used 195/65-R15

Thanks for that lesson, Nick.I presume wheels are shaped so that tyre centre lines coincide with the steering centre lines (the 'offset?).If Omega steel spare wheels will fit my Vectra, I reckon all Omega wheels should do so. Right?

It's more complicated than that; ideally you want the tyre to rotate around the centre patch but there are lots of other considerations. Anyone designing a suspension system from scratch will start with the wheel and tyre and work from there. It's really critical to get them right.

Omega wheels will bolt on, but might not work.

You can't use 17" Omega wheels on an Astra G for instance. If you're no longer keeping Omegas, then get rid of the bits and use the correct ones for the replacement cars. Using old tyres(like 20 year old spares) is a very bad idea, no matter how 'as new' they look

205/65-R15 94V on 6.1/2J X 15" (ET 33) steel is the standard spare for facelift estates.A wider tyre or a wider rim would not fit in the wheel-well.

That is not true: a 17" Elite wheel with inflated 235/45 tyre fits the wheel-well just fine. It's a very tight fit on height though, some spacers are required for the boot floor latch to work. I never bothered on mine because gravity holds it down OK, and my car had a fitted rubber load mat that helped.

Thanks for that lesson, Nick.I presume wheels are shaped so that tyre centre lines coincide with the steering centre lines (the 'offset?).If Omega steel spare wheels will fit my Vectra, I reckon all Omega wheels should do so. Right?

It's more complicated than that; ideally you want the tyre to rotate around the centre patch but there are lots of other considerations. Anyone designing a suspension system from scratch will start with the wheel and tyre and work from there. It's really critical to get them right.

Omega wheels will bolt on, but might not work.

You can't use 17" Omega wheels on an Astra G for instance. If you're no longer keeping Omegas, then get rid of the bits and use the correct ones for the replacement cars. Using old tyres(like 20 year old spares) is a very bad idea, no matter how 'as new' they look

I can see that too wide a tyre might foul bodywork on full lock, and Carlton wheels don't go over Omega hubs/brake drums. Otherwise, I can't imagine the complications.Steel wheels are stronger and cheaper than alloy wheels, easier to fit, and no heavier. I reckon alloy wheels are silly fashion items.

I can see that too wide a tyre might foul bodywork on full lock, and Carlton wheels don't go over Omega hubs/brake drums. Otherwise, I can't imagine the complications.

Steel wheels are stronger and cheaper than alloy wheels, easier to fit, and no heavier. I reckon alloy wheels are silly fashion items.

There's a load of stuff that has to fit inside the wheel, and the steering movement has to be allowed for. Add the suspension travel, and the inside clearance is much more complicated than the bodywork.

Steel wheels aren't necessarily any of the things you listed, but they do get more likely the bigger and wider the wheels. especially when the mounting face is closer to one edge than the centre of the wheel.

Not so long ago Jaguars, MGs and Aston Martins had wire wheels. I've never driven one, and I can't imagine they had any offset, but they must have worked after a fashion.

They do. But they're ugly, fragile and expensive which is why they went out of fashion.

I stand corrected, I read they do make offset wire wheels, with different length spokes inside and outside. I suppose again they were fashion items, and as you say, expensive and fragile, and have now passed out of fashion. Not so good with tubeless tyres either.